Theoretical studies on NLO properties of push-pull multi-cycle electro-optical polymer intermediates including thiophene ring

The second-order nonlinear optical susceptibilities beta (muk), beta (mu) a nd third-order non-linear optical susceptibilities gamma (mu k1), [gamma] o f a series of the novel push-pull multi-ring electro-photo polymer intermed iates have been calculated. The influences of molecular structure, donor, a cceptor and the frequency of external field on beta and gamma, and the rela tionship between gamma and the number of thiophene rings (i. e. conjugated chain length) have been studied using INDO/SCI methods combined with sum-ov er-state (SOS) formula. The calculated results show that gamma is proportio nal to 2.69 power of the chain length of the conjugated molecular bowls whe n the length is not quite long.